In Groves and Heeringa 's original formulation, responsive design proceeds in phases. They define these phases as: "A design phase is a time period of a data collection during which the same set of sampling frame, mode of data collection, sample design, recruitment protocols and measurement conditions are extant." (page 440). These responsive design phases are different than the two-phase sampling defined by Hansen and Hurwitz. Hansen and Hurwitz assumed 100% response so there was no nonresponse bias. There two-phase sampling was all about minimizing variance for a fixed budget. Groves and Heeringa, on the other hand, live in a world where nonresponse does occur. They seek to control it through phases that recruit complementary groups of respondents. The goal is that the nonresponse biases from each phase will cancel each other out. The focus on bias is a new feature relative to Hansen and Hurwitz. A question in my mind about the phases is how the...
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